The world's last naturally occurring case of smallpox was in Somalia in 1977. But the White House fears that Iraqi leader Saddam Hussein has supplies of the virus and may be capable of unleashing it on an invading army.

"Smallpox is a potentially fatal illness, killing about 30 percent of those infected," said Navy Capt. Konrad Hayashi, a physician. A large percentage of those who survive the disease wind up blind or disfigured, he added.

The vaccination is mandatory for the 45,000 members of the 1st Marine Expeditionary Force, except those who have medical conditions that prevent them from getting the vaccination, Hayashi said.

"We make sure anybody who has an immune deficiency will not get the vaccine," Hayashi said.

The smallpox vaccine is not injected with a hypodermic syringe. The vaccination is administered by a two-pronged needle that is dipped into the vaccine solution. The needle is used to puncture the skin a few times, leaving the solution beneath the surface.

The smallpox vaccine contains a live virus called Vaccinia, which is related to smallpox but milder and helps the body develop immunity.

"The only reaction I've had is some itching," said Navy Cmdr. Richard Dowling, a physician who was vaccinated Monday. The vaccine had formed a pink pustule on his upper arm.

Dowling said the risk of serious side effects from the vaccine are remote. One or two people of 1 million vaccinated may die, he said, and 17 to 40 out of 100,000 experience serious side effects. Those include an allergic reaction or a rash that spreads to other parts of the body.

Because the pustule formed by the vaccination is contagious, those who have close contact with family members who may experience ill effects from the vaccine also were exempt.

Navy corpsman Paul Kane, a 2nd class petty officer assisting with the inoculations, said he is exempt because his daughter has eczema.

"If you have eczema or a (family member) has eczema, the live virus can go to that break in the skin and cause blistering," Kane said.

He said he likely will be vaccinated if he is deployed.

Most of the Marines and sailors interviewed yesterday said they were in favor of the vaccine and knew of no one who resisted it. Hayashi said those who resist the vaccine will be "re-educated," and if they still refuse they face punishment.

One member of the 1st Marine Expeditionary Force who is exempt from the vaccine said yesterday that he would refuse it.

"I personally feel like (smallpox) is not that big of a threat," he said on condition of anonymity. "If I'm going to die, it's going to happen; I don't care if it's because I didn't take a vaccination."

Some military and health experts agree it is unlikely the virus can be used as a weapon.

Routine vaccination against smallpox was stopped after the disease was eliminated from the world's population.

The 1st Marine Expeditionary Force includes troops from Camp Pendleton, Miramar Marine Corps Air Station's 3rd Air Wing and Marine bases in Twentynine Palms and Yuma, Ariz.